A new DNase was found to be iduced in Epstein-Barr virus (EBV) superinfected Raji cells or iododeoxyuride (IUdR) induced D98/HR-1 cells. The induced DNase has a unique electrophoretic mobility as well as immunospecificity. Thymidine kinase (TK) was not found to be induced in either EBV infected or IUdR induced cells under the same conditions. The activity of TK present in IRdR induced D98/HR-1 or superinfected Raji or TK Raji cells did not have differences in the electrophoretic profile, binding on a TK affinity column, sensitivity to 5-propyl UdR, dCTP and dTTP inhibitors, when compared to control cells. Confirmation of an EBV associated DNA polymerase was also obtained and was used as an internal control for virus replication in these experiments. We have used man/mouse somatic cell hybrid cells to study the association of the EBV genome and cell genome. Attempts were made to identify a specific human chromosome(s) with which the EBV genome is associated. Our data suggest that at least in the Burkitt/mouse hybrid combination studied, the EBV genome is not associated with any specific human chromosome.